The improvement of Fischer-Tropsch (F-T) catalysts, i.e., catalysts useful for the production of petrochemicals and liquid transportation fuels by hydrogenation of carbon monoxide, has been the subject of ongoing research for some years; and this work continues. Early commercial work with the F-T process began in Germany in the 1920's, and was continued, resulting in the SASOL plants of South Africa. F-T synthesis is well documented in the technical and patent literature. The Group VIII metals, e.g., ruthenium and the Iron Group Metals such as iron and cobalt, have been used extensively as catalytic metals in the production of F-T catalysts, and these metals have been promoted or modified with various other metals, and supported on various substrates in formation of the catalysts.
Cobalt catalysts, particularly the promoted cobalt catalysts, e.g., those constituted of cobalt and rhenium, or cobalt, thoria and rhenium, supported on titania, or other titania-containing support have been found to exhibit high selectivity in the conversion of methanol to hydrocarbon liquids, or synthesis of hydrocarbon liquids from hydrogen and carbon monoxide as disclosed, e.g., in U.S. Pat. No. 4,568,663. The catalysts can be prepared by gellation or cogellation techniques, but typically they are prepared by deposition of the metal, or metals, on the previously pilled, pelleted, beaded, extruded, or sieved support material, or a powder by the impregnation method. In preparing the composite catalysts, the metals are deposited from solution on the support in preselected amounts to provide the desired absolute amounts and weight ratio of the respective metals, e.g., cobalt and rhenium. Suitably, e.g., the cobalt and rhenium are composited with the support by contacting the support with a solution of a cobalt-containing compound, or salt, or a rhenium-containing compound, or salt, e.g., a nitrate, carbonate or the like. Optionally, cobalt and rhenium can be co-impregnated upon the support. The cobalt and rhenium compounds used in the impregnation can be any organometallic or inorganic compounds which decompose to give cobalt and rhenium oxides upon calcination, such as a cobalt, or rhenium nitrate, acetate, acetylacetonate, naphthenate, carbonyl, or the like. The amount of impregnation solution used should be sufficient to impregnate the catalyst via the incipient wetness technique, or sufficient to completely immerse the carrier, usually a volume of liquid ranging from about 1 to 20 times of the carrier by volume, depending on the metal, or metals, concentration in the impregnation solution. The impregnation treatment can be carried out under a wide range of conditions including ambient or elevated temperatures. The catalyst, after impregnation, is dried, and calcined; suitably by contact with oxygen, air or other oxygen-containing gas at temperature sufficient to oxidize the metal, or metals; e.g., to convert cobalt to Co.sub.3 O.sub.4. The catalyst, or catalyst precursor, is then reduced and activated by contact of the oxidized metal, or metals, with hydrogen, or hydrogen-containing gas.
The reduced catalysts, e.g., cobalt catalyst, and cobalt catalyst promoted with other metals, have been found to provide relatively high selectivity, activity and activity maintenance in methanol conversion, and in the conversion of hydrogen and carbon monoxide to distillate fuels; predominantly C.sub.5 + linear paraffins and olefins, with low concentrations of oxygenates. Nonetheless, there remains a pressing need for F-T catalysts of yet higher activity; particularly more active catalysts capable of producing transportation fuels and lubricants of high quality at good selectivity and high levels of productivity.